1. Field of the Invention
The invention relates to an MEMS (micro-electro-mechanical-system) microphone package, and more particularly to an MEMS microphone package with an RF insensitive MEMS microphone chip.
2. Description of the Related Art
Referring to FIG. 1, a conventional MEMS (micro-electro-mechanical-system) microphone package includes a substrate 102, a metal cap 101 attached to the substrate 102, an MEMS microphone die 103 mounted on the substrate 102, and a readout IC (integrated circuit) chip 104 also mounted on the substrate 102.
The metal cap 101 has a sound inlet 106 through which the MEMS microphone die 103 receives external sound. The MEMS microphone die 103 includes a diaphragm and a back plate. The diaphragm vibrates according to the variation of sound pressure. The diaphragm and the back plate form a capacitor and the capacitance thereof is inverse proportional to the space between the diaphragm and the back plate.
A bonding wire 105 is connected between the MEMS microphone die 103 and the readout IC chip 104. The readout IC chip 104 provides bias voltage (around 12V) to bias the diaphragm and is capable of driving external low-impedance loading.
The metal cap 101 and the substrate 102 constitute a means for shielding, to protect the MEMS microphone die 103 from RF (radio frequency) interference.